HFS+, or Hierarchical File System Plus, is the file system designed by Apple Computer[www.apple.com] to supersede HFS. First introduced with Mac OS 8.1, one of the biggest differences was the lower allocation block size of 4kb, thereby increasing performance and lowering fragmentation [http://developer.apple.com/technotes/tn/tn1121.html#HFSPlus].

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HFS+, or Hierarchical File System Plus, is the file system designed by Apple Computer[http://www.apple.com] to supersede HFS. First introduced with Mac OS 8.1, one of the biggest differences was the lower allocation block size of 4kb, thereby increasing performance and lowering fragmentation [http://developer.apple.com/technotes/tn/tn1121.html#HFSPlus].

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There are structurally many differences between HFS and HFS+, which are listed below[http://developer.apple.com/technotes/tn/tn1150.html#HFSPlusBasics]:

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<CENTER><TABLE Border=1 cellpadding=2 cellspacing=0>

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<TR>

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<TD>

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<P><B>Feature</B></p>

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+

</TD><TD>

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<P><B>HFS</B></p>

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</TD><TD>

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<P><B>HFS Plus</B></p>

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</TD><TD>

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<P><B>Benefit/Comment</B></p>

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</TD></TR>

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<TR>

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<TD>

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<P>User visible name</p>

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</TD><TD>

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<P>Mac OS Standard</p>

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</TD><TD>

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<P>Mac OS Extended</p>

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</TD><TD>

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<P></p>

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</TD></TR>

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<TR>

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<TD>

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<P>Number of allocation blocks</p>

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</TD><TD>

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<P>16 bits worth</p>

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</TD><TD>

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<P>32 bits worth</p>

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</TD><TD>

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<P>Radical decrease in disk space used on large

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volumes, and a larger number of files per volume.</p>

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</TD></TR>

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<TR>

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<TD>

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<P>Long file names</p>

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</TD><TD>

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<P>31 characters</p>

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</TD><TD>

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<P>255 characters</p>

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</TD><TD>

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<P>Obvious user benefit; also improves

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cross-platform compatibility</p>

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</TD></TR>

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<TR>

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<TD>

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<P>File name encoding</p>

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</TD><TD>

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<P>MacRoman</p>

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</TD><TD>

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<P>Unicode</p>

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</TD><TD>

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<P>Allows for international-friendly file names,

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including mixed script names</p>

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</TD></TR>

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<TR>

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<TD>

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<P>File/folder attributes</p>

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</TD><TD>

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<P>Support for fixed size attributes (FileInfo and

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ExtendedFileInfo)</p>

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</TD><TD>

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<P>Allows for future meta-data extensions</p>

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</TD><TD>

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<P>Future systems may use metadata for a richer

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Finder experience</p>

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</TD></TR>

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<TR>

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<TD>

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<P>OS startup support</p>

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</TD><TD>

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<P>System Folder ID</p>

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</TD><TD>

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<P>Also supports a dedicated startup file</p>

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</TD><TD>

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<P>May help non-Mac OS systems to boot from HFS

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Plus volumes</p>

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</TD></TR>

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<TR>

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<TD>

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<P>catalog node size</p>

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</TD><TD>

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<P>512 bytes</p>

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</TD><TD>

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<P>4 KB</p>

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</TD><TD>

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<P>Maintains efficiency in the face of the other

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changes. (This larger catalog node size is due to

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the much longer file names [512 bytes as opposed to

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32 bytes], and larger catalog records (because of

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more/larger fields)).</p>

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</TD></TR>

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<TR>

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<TD>

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<P>Maximum file size</p>

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</TD><TD>

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<P>2<SUP>31</SUP> bytes</p>

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</TD><TD>

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<P>2<SUP>63</SUP> bytes</p>

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</TD><TD>

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<P>Obvious user benefit, especially for multimedia

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content creators.</p></td>

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</tr>

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</table></CENTER>

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<br>

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An HFS+ volume contains five special files that are necessary to the file system:

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<nl>

+

<li>

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Catalog file

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</li>

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<li>Extents overflow file

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</li>

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<li>

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Allocation file

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</li>

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<li>Attributes file

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</li>

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<li>

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Startup file

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</li>

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</nl>

Revision as of 23:37, 28 November 2006

HFS+, or Hierarchical File System Plus, is the file system designed by Apple Computer[1] to supersede HFS. First introduced with Mac OS 8.1, one of the biggest differences was the lower allocation block size of 4kb, thereby increasing performance and lowering fragmentation [2].

There are structurally many differences between HFS and HFS+, which are listed below[3]:

Feature

HFS

HFS Plus

Benefit/Comment

User visible name

Mac OS Standard

Mac OS Extended

Number of allocation blocks

16 bits worth

32 bits worth

Radical decrease in disk space used on large
volumes, and a larger number of files per volume.

Maintains efficiency in the face of the other
changes. (This larger catalog node size is due to
the much longer file names [512 bytes as opposed to
32 bytes], and larger catalog records (because of
more/larger fields)).

Maximum file size

231 bytes

263 bytes

Obvious user benefit, especially for multimedia
content creators.

An HFS+ volume contains five special files that are necessary to the file system:
<nl>